[clang] [clang][DependencyScanning] Implementation of `CompilerInstanceWithContext` to Improve By-Name Queries (PR #164345)

[Ben Langmuir via cfe-commits]

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@@ -339,6 +341,10 @@ class ModuleDepCollector final : public DependencyCollector {
   std::optional<P1689ModuleInfo> ProvidedStdCXXModule;
   std::vector<P1689ModuleInfo> RequiredStdCXXModules;
 
+  /// A pointer to the preprocessor callback so we can invoke it directly
+  /// if needed.
+  ModuleDepCollectorPP *CollectorPPPtr = nullptr;
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benlangmuir wrote:

Could we add a brief note to the doc comment about this? I would just say something like
> Owned by the PPCallbacks instance.

https://github.com/llvm/llvm-project/pull/164345